DE OS 3 720 325 and its equivalent U.S. Pat. No. 4,938,605 discloses the production of a so-called filler-master batch, in which the components of a mixture are first premixed in a two-stage mixing process and the thus-obtained intermediate product further mixed in a twin-screw mixing and kneading machine known as a Z-type kneader and then the mixed product is discharged by a screw extending at the bottom of the mixing tank to a discharge cylinder.
The plastics, which are present in powder or liquid form as initial materials, are introduced with pre-measured amounts of filler into a mixing and kneading machine, serving as a preliminary stage in order to mix and distribute the fillers into the low-viscous or molten plastics.
In contrast to this relatively expensive procedure, it is often possible to effect melting of the plasticizable compounds and mixing of the fillers therein in a single mixing process.
It is also known to first melt the plasticizable compounds in a mixing and kneading machine, such as in a Z-type kneader, and then to mix the filler or reinforcing material into the plastic melt. In order to effect melting of the plasticizable compound in the kneading machine, a sufficient heat transfer from the heatable kneading machine to the mixed material must be provided, while a small portion of heat is introduced into the plasticizable compound by shearing energy via the mixing blades of the kneader.
This procedure, however, not only requires a high energy input, but the quality of the produced plastic product is not always satisfactory.